Determining the exact altitude of a receiver can be quite challenging where typical positioning solutions are not reliable. Imprecise estimates of the receiver's altitude may have “life or death” consequences for the user. For example, an imprecise altitude estimate of a mobile phone operated by a user calling 911 can delay emergency response times when responding to the call, mainly because the imprecise altitude estimate can only narrow the user's position to several adjacent floors in a building instead of the exact floor at which the user is experiencing an emergency. In less dire situations, imprecise estimates of the user's position can negatively impact efforts to provide navigation to a desired destination.
Various solutions exist to estimate the altitude of a receiver, including the solution detailed by U.S. Patent Application Publication No. US 2012/0182180, published Jul. 19, 2012, which uses measurements of pressure from a network of pressure sensors and a measurement of pressure from the receiver to estimate the receiver's altitude. However, such solutions require pressure sensors that measure pressure within a tolerated error from true pressure (e.g. usually a tolerated error of no more than 10 Pascals for floor-level accuracy). Unfortunately, the pressure sensors in the network are often unstable and known to drift above the tolerated error. Thus, cost-effective approaches are needed to calibrate these unstable sensors so they produce measurements within the tolerated error from true pressure.